This study evaluated the association between receipt of atypical antipsychotics and outcomes of skilled NH patients admitted with hip fracture with and without delirium symptomatology. Among residents with no evidence of delirium symptomatology on admission, those who received antipsychotics had an increased likelihood of death prior to discharge, were more likely to stay longer in NHs, and had less functional improvement.
Among residents showing symptoms of delirium upon admission, those who received antipsychotics did not have statistically different outcomes. In other words, treating presumed delirium for patients with hip fracture with antipsychotics did not appear to benefit these individuals. Rather, antipsychotic use was associated with adverse outcomes for subsyndromal delirium patients, such as a lower likelihood of being discharged home.
The strengths of this study were its use of a nationally representative data source, rigorous statistical tools in the analysis with a homogeneous study population, and examination of clinically and economically important outcomes. All regression models controlled for an expansive set of confounders, in addition to temporal trends. Propensity score reweighting addressed the possibility of selection bias. Facility heterogeneity, such as antipsychotic prescribing culture, was dealt with using facility and time fixed effects. A second major strength is the examination of a skilled NH population that is not easily captured based on secondary data claims such as Medicare Part D. Such claims are limited in their ability to capture medication utilization in the acute-care hospital and skilled NH settings due to the bundling of payments under Medicare. By matching MDS data with the Medicare enrollment file, however, we were able to identify NH admissions and associated use of antipsychotics.
Several limitations warrant discussion. It is important to note that this exploratory study tests for associations rather than causal inferences. Primary data collection will likely be needed to ascertain whether antipsychotic use alone is responsible for the adverse outcomes described here or whether residual comorbidities are contributing factors. Additionally, data is needed to ascertain whether the effects of specific antipsychotic drugs, dosages and/or duration of use affect outcomes differentially.29
Secondly, we utilized a methodology (NH-CAM) for identifying delirium-like symptoms that has not been validated independently against gold standard diagnostic tools. Although prior studies suggest that the NH-CAM performs well against other commonly used MDS 2.0 tools for identifying delirium including the triggers for the Delirium Resident Assessment Protocol,14
it is not our intention to presume that residents at various stages of the NH-CAM had clinically defined delirium. Rather, this tool merely implies that they have increased gradations of delirium-like symptoms. Additionally, though care was taken to exclude the confounding effect of dementia within the NH-CAM and in our study, it remains possible that this has influenced our results.30
Finally, though the MDS has been shown to be a reliable data source for numerous items,12, 13
we were not able to access the associated hospital claims for study participants. For instance, we relied on MDS diagnoses to identify hip fracture patients. To assess the validity of this approach, we performed a subset analysis of Medicare hospital claims from 2006 and compared hip fracture ICD-9-CM codes (820.X) to the initial MDS assessments from subsequent NH admissions. The estimated positive predictive value was 78.7% (95% CI, 78.3-79.0), indicating a reasonably high reliability to predict hip fracture. Nevertheless, it does indicate that the MDS might incorrectly identify some with hip fracture. If false positives were more likely among cognitively impaired patients, who were more prevalent in one group, this would have introduced bias. Clinically, however, there is no reason to presume that this would occur.